EP2907888A1 - Compressor blade with erosion resistant hard material coating - Google Patents

Abstract

The invention introduces a compressor blade (1) for a gas turbine (100). The compressor blade (1) has a blade substrate (2) which consists of a metal alloy and has an aluminum diffusion zone (3) on a surface of the blade substrate (2). In addition, the compressor blade (1) has a hard material coating (4) arranged on the surface of the blade substrate (2). Further aspects of the invention relate to a compressor (105) with such a compressor blade (1) and a production method for such a compressor blade (1).

Description

Technical area

The invention relates to a compressor blade for a gas turbine, a compressor with such a compressor blade and a manufacturing method for such a compressor blade.

Technical background

In the case of gas turbines, water is introduced into the combustion air compressed by a compressor as part of the so-called "wet compression", which leads to an increase in the efficiency of the gas turbine due to the cooling effect thereby caused and the increase in the mass flow in the gas turbine. The water is atomized as finely as possible, but due to the drops in the combustion air, erosion occurs on the compressor blades. In addition, the moisture causes increased corrosion. So far, compressor blades have been coated with anti-corrosion coatings such as Sicoat 8610, but they do not provide adequate erosion protection. The object of the invention is therefore to introduce a robust compressor blade which can withstand the increased erosion load during the wet compression process for a longer time.

Summary of the invention

The invention therefore introduces a compressor blade for a gas turbine. The compressor blade has a blade substrate made of a metal alloy and having an aluminum diffusion zone on a surface of the blade substrate. In addition, the compressor blade has a arranged on the surface of the blade substrate hard material coating.

The compressor blade according to the invention has the advantage of greater erosion resistance due to the hard material coating applied to the blade substrate. The hard coating also offers corrosion protection. The problem with such hard coatings, however, is that they can chip off locally. As a result, at such an exposed point of the blade substrate corrosion can be used, which favors the further spalling of the hard material coating by undercorrosion. By chipping the compressor blade is finally revealed to erosion. The invention solves this problem by an aluminum diffusion layer; The aluminum contained in this aluminum diffusion layer reacts with chipping of the hard coating to aluminum oxide, which protects the metal alloy of the blade substrate from corrosion. Undercutting, which can lead to a blade breakage, is prevented in this way.

The hard material coating preferably consists of TiN, TiAlN, AlTiN, CrN as monolayer or multilayer ceramics or contains TiN, TiAlN, AlTiN, CrN as monolayer or multilayer ceramics. As a hard material coating, these materials offer a particularly high resistance to erosion and corrosion loads.

The aluminum diffusion zone may have a thickness of 10 to 30 micrometers, preferably 15 to 25 micrometers. An aluminum diffusion zone of about 20 microns thick can accommodate enough aluminum to protect the hard coated compressor blade of the present invention from corrosion for at least 100,000 hours of operation.

The aluminum diffusion zone of the compressor blade may have an aluminum content of 0.05 to 0.2 weight percent, preferably 0.075 to 0.15 weight percent. An aluminum content of about 0.1 weight percent provides enough aluminum to provide reliable corrosion protection To ensure inventive hard-coated compressor blade. However, the person skilled in the art can determine suitable layer thicknesses, aluminum proportions and / or diffusion profiles as a function of the respective operating conditions by modeling for the respective individual case.

The metal alloy of the compressor blade is preferably a creep-resistant steel, for example a creep-resistant steel according to EN 10302: 2008. An example of a suitable steel is X22CrNiMoV12-1. Creep resistant steels are a low cost material that can withstand the high mechanical stresses experienced by a compressor blade of a gas turbine during operation at the moderate temperatures prevailing there.

A second aspect of the invention relates to a compressor for a gas turbine comprising a plurality of compressor blades, of which at least one compressor blade according to the first aspect of the invention is formed.

The plurality of compressor blades may be arranged in a plurality of rows, each row having a plurality of compressor blades arranged transverse to a main flow direction of the compressor. In addition, the rows may be arranged adjacent to the main flow direction. Preferably, the compressor blades of the first to fourth row of compressor blades according to the first aspect of the invention are formed along the main flow direction. The compressor blades of the first to fourth rows of the compressor are the most exposed to erosion, which is why the compressor blades according to the invention can be used particularly advantageously here.

• -- Bereitstellen eines Schaufelsubstrates aus einer Metalllegierung;
• -- Eindiffundieren von Aluminium in eine Oberflächenzone des Schaufelsubstrates; und
• -- Beschichten des Schaufelsubstrates mit einer Hartstoffbeschichtung.

Another aspect of the invention introduces a manufacturing method for a compressor blade according to the invention. The process has at least the following steps:

• - Providing a blade substrate made of a metal alloy;
• - diffusing aluminum into a surface zone of the blade substrate; and
• - Coating of the blade substrate with a hard material coating.

Preferably, in the step of diffusing aluminum into the surface zone, an aluminum diffusion zone having a thickness of 10 to 30 micrometers, preferably 15 to 25 micrometers, is produced.

In an advantageous embodiment of the method according to the invention, the step of diffusing aluminum into the surface zone is carried out such that an aluminum content of 0.05 to 0.2 weight percent, preferably 0.075 to 0.15 weight percent, is present in the surface zone.

In the step of coating the blade substrate with a hard coating, a step of physical vapor deposition or thermal plasma spraying may be performed.

Brief description of the pictures

• Figur 1 ein Beispiel einer Gasturbine 100 in einem Längsteilschnitt;
• Figur 2 eine Laufschaufel oder Leitschaufel einer Gasturbine-ne in perspektivischer Ansicht;
• Figur 3 eine Brennkammer einer Gasturbine; und
• Figur 4 eine Teilansicht eines Querschnitts durch eine erfindungsgemäße Verdichterschaufel.

The invention will be explained in more detail with reference to illustrations of exemplary embodiments. Show it:

• FIG. 1 an example of a gas turbine 100 in a longitudinal partial section;
• FIG. 2 a blade or vane of a gas turbine ne in a perspective view;
• FIG. 3 a combustion chamber of a gas turbine; and
• FIG. 4 a partial view of a cross section through a compressor blade according to the invention.

Detailed description of the pictures

The FIG. 1 shows by way of example a gas turbine 100 in a longitudinal partial section.

The gas turbine 100 has inside a rotatably mounted about a rotation axis 102 rotor 103 with a shaft 101, which is also referred to as a turbine runner.

Along the rotor 103 follow one another an intake housing 104, a compressor 105, for example, a toroidal combustion chamber 110, in particular annular combustion chamber, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109th

The annular combustion chamber 110 communicates with an annular annular hot gas channel 111, for example. There, for example, four turbine stages 112 connected in series form the turbine 108.

Each turbine stage 112 is formed, for example, from two blade rings. As seen in the direction of flow of a working medium 113, in the hot gas channel 111 of a row of guide vanes 115, a series 125 formed of rotor blades 120 follows.

The guide vanes 130 are fastened to an inner housing 138 of a stator 143, whereas the moving blades 120 of a row 125 are attached to the rotor 103 by means of a turbine disk 133, for example.

Coupled to the rotor 103 is a generator or work machine (not shown).

During operation of the gas turbine 100, air 105 is sucked in and compressed by the compressor 105 through the intake housing 104. The compressed air provided at the turbine-side end of the compressor 105 is supplied to the burners 107 where it is mixed with a fuel. The mixture is then burned to form the working fluid 113 in the combustion chamber 110. From there, the working medium 113 flows along the hot gas channel 111 past the guide vanes 130 and the rotor blades 120. On the rotor blades 120, the working medium 113 expands in a pulse-transmitting manner so that the rotor blades 120 drive the rotor 103 and drive the machine coupled to it.

The components exposed to the hot working medium 113 are subject to thermal loads during operation of the gas turbine 100. The guide vanes 130 and rotor blades 120 of the first turbine stage 112, viewed in the flow direction of the working medium 113, are subjected to the greatest thermal stress in addition to the heat shield elements lining the annular combustion chamber 110.

To withstand the prevailing temperatures, they can be cooled by means of a coolant.

Likewise, substrates of the components may have a directional structure, i. they are monocrystalline (SX structure) or have only longitudinal grains (DS structure).

As the material for the components, in particular for the turbine blade 120, 130 and components of the combustion chamber 110, for example, iron-, nickel- or cobalt-based superalloys are used.

Such superalloys are for example from EP 1 204 776 B1 . EP 1 306 454 . EP 1 319 729 A1 . WO 99/67435 or WO 00/44949 known.

Also, the blades 120, 130 may be anti-corrosion coatings (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and is yttrium (Y) and / or silicon , Scandium (Sc) and / or at least one element of the rare earth or hafnium). Such alloys are known from the EP 0 486 489 B1 . EP 0 786 017 B1 . EP 0 412 397 B1 or EP 1 306 454 A1 ,

On the MCrAlX, a thermal barrier coating may still be present, consisting for example of ZrO2, Y2O3-ZrO2, i. it is not, partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide.

By suitable coating methods, e.g. Electron beam evaporation (EB-PVD) produces stalk-shaped grains in the thermal barrier coating.

The vane 130 has a guide vane foot (not shown here) facing the inner housing 138 of the turbine 108 and a vane head opposite the vane foot. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

FIG. 2 shows a perspective view of a blade 120 or guide vane 130 of a turbomachine, which extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or a power plant for power generation, a steam turbine or a compressor.

The blade 120, 130 has along the longitudinal axis 121 consecutively a fastening region 400, a blade platform 403 adjacent thereto and an airfoil 406 and a blade tip 415.

As a guide blade 130, the blade 130 may have at its blade tip 415 another platform (not shown).

In the mounting region 400, a blade root 183 is formed, which serves for attachment of the blades 120, 130 to a shaft or a disc (not shown).

The blade root 183 is designed, for example, as a hammer head. Other designs as Christmas tree or Schwalbenschwanzfuß are possible.

The blade 120, 130 has a leading edge 409 and a trailing or trailing edge 412 for a medium flowing past the airfoil 406.

In conventional blades 120, 130, for example, solid metallic materials, in particular superalloys, are used in all regions 400, 403, 406 of the blade 120, 130.

Such superalloys are for example from EP 1 204 776 B1 . EP 1 306 454 . EP 1 319 729 A1 . WO 99/67435 or WO 00/44949 known.

The blade 120, 130 can be made by a casting process, also by directional solidification, by a forging process, by a milling process or combinations thereof.

Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed to high mechanical, thermal and / or chemical stresses during operation.

The production of such monocrystalline workpieces, for example, by directed solidification from the melt. These are casting processes in which the liquid metallic alloy to monocrystalline structure, ie the single-crystal workpiece, or directionally solidified.

Here, dendritic crystals are aligned along the heat flow and form either a columnar grain structure (columnar, i.e. grains that run the full length of the workpiece and here, in common usage, are referred to as directionally solidified) or a monocrystalline structure, i. the whole workpiece consists of a single crystal. In these processes, one must avoid the transition to globulitic (polycrystalline) solidification, since non-directional growth necessarily forms transverse and longitudinal grain boundaries which negate the good properties of the directionally solidified or monocrystalline component.

The term generally refers to directionally solidified microstructures, which means both single crystals that have no grain boundaries or at most small angle grain boundaries, and stem crystal structures that have probably longitudinal grain boundaries but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures.

Such methods are known from U.S. Patent 6,024,792 and the EP 0 892 090 A1 known.

Likewise, the blades 120, 130 may have coatings against corrosion or oxidation, e.g. M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare ones Earth, or hafnium (Hf)). Such alloys are known from the EP 0 486 489 B1 . EP 0 786 017 B1 . EP 0 412 397 B1 or EP 1 306 454 A1 ,

The density is preferably 95% of the theoretical density.

A protective aluminum oxide layer (TGO = thermal grown oxide layer) is formed on the MCrAlX layer (as an intermediate layer or as the outermost layer).

Preferably, the layer composition comprises Co-30Ni-28Cr-8Al-0.6Y-0.7Si or Co-28Ni-24Cr-10Al-0.6Y. Besides these cobalt-based protective coatings, nickel-based protective layers such as Ni-10Cr-12Al-0.6Y-3Re or Ni-12Co-21Cr-11Al-0.4Y-2Re or Ni-25Co-17Cr-10A1-0,4Y-1 are also preferably used , 5RE.

On the MCrAlX can still be present a thermal barrier coating, which is preferably the outermost layer, and consists for example of ZrO2, Y2O3-ZrO2, ie it is not, partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide.
The thermal barrier coating covers the entire MCrAlX layer.

By suitable coating methods, e.g. Electron beam evaporation (EB-PVD) produces stalk-shaped grains in the thermal barrier coating.

Other coating methods are conceivable, e.g. Atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier coating may have porous, micro- or macro-cracked grains for better thermal shock resistance. The thermal barrier coating is therefore preferably more porous than the MCrAlX layer.

Refurbishment means that components 120, 130 may have to be freed of protective layers after use (eg by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. Optionally, even cracks in the component 120, 130 are repaired. Thereafter, a recoating occurs of the component 120, 130 and a renewed use of the component 120, 130.

The blade 120, 130 may be hollow or solid. If the blade 120, 130 is to be cooled, it is at least partially hollow and may still have film cooling holes 418 (indicated by dashed lines).

The FIG. 3 shows a combustion chamber 110 of a gas turbine. The combustion chamber 110 is designed, for example, as a so-called annular combustion chamber, in which a plurality of burners 107 arranged around a rotation axis 102 in the circumferential direction open into a common combustion chamber space 154, which generate flames 156. For this purpose, the combustion chamber 110 is configured in its entirety as an annular structure, which is positioned around the axis of rotation 102 around.

To achieve a comparatively high efficiency, the combustion chamber 110 is designed for a comparatively high temperature of the working medium M of about 1000 C to 1600 C. In order to allow a comparatively long service life even in these operating parameters, which are unfavorable for the materials, the combustion chamber wall 153 is provided on its side facing the working medium M with an inner lining formed of heat shield elements 155.

Each heat shield element 155 made of an alloy is equipped on the working medium side with a particularly heat-resistant protective layer (MCrAlX layer and / or ceramic coating) or is made of highly temperature-resistant material (solid ceramic stones).

These protective layers may be similar to the turbine blades, so for example MCrAlX means: M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare earths, or hafnium (Hf). Such alloys are known from the EP 0 486 489 B1 . EP 0 786 017 B1 . EP 0 412 397 B1 or EP 1 306 454 A1 ,

On the MCrAlX may still be present, for example, a ceramic thermal barrier coating and consists for example of ZrO2, Y2O3-ZrO2, i. it is not, partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide.

By suitable coating methods, e.g. Electron beam evaporation (EB-PVD) produces stalk-shaped grains in the thermal barrier coating.

Other coating methods are conceivable, e.g. atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier coating may have porous, micro- or macro-cracked grains for better thermal shock resistance.

Refurbishment means that heat shield elements 155 may need to be deprotected (e.g., by sandblasting) after use. This is followed by removal of the corrosion and / or oxidation layers or products. If necessary, cracks in the heat shield element 155 are also repaired. This is followed by a recoating of the heat shield elements 155 and a renewed use of the heat shield elements 155.

Due to the high temperatures inside the combustion chamber 110 may also be provided for the heat shield elements 155 and for their holding elements, a cooling system. The heat shield elements 155 are then, for example, hollow and possibly still have cooling holes (not shown) which open into the combustion chamber space 154.

FIG. 4 shows a partial view of a cross section through a compressor blade according to the invention 1. The compressor blade 1 has a blade substrate 2, which is made of a metal alloy and the aerodynamic shape of Compressor bucket determined. On the surface of the blade substrate 2, an aluminum diffusion layer 3 is provided, which was produced by diffusing aluminum into the blade substrate 2. The aluminum diffusion layer 3 may have a thickness of about 20 micrometers and an aluminum content of about 0.1 weight percent aluminum. After the aluminum diffusion layer 3 is formed, a hard coating 4 is applied to the blade substrate. This can be done for example by a deposition from the gas phase, for example by physical vapor deposition. The hard material coating 4 protects the compressor blade 1 against erosion and corrosion. If a part of the hard material coating 4 breaks off, the aluminum of the aluminum diffusion layer exposed in this way reacts to aluminum oxide, which prevents corrosion of the exposed point of the blade substrate 2 and thereby further spalling of the hard material coating 4 which is promoted by undercorrosion of the adjacent surface areas.

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples. Variations thereof may be derived by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims (11)

A compressor blade (1) for a gas turbine (100) and with a blade substrate (2) consisting of a metal alloy and having on one surface of the blade substrate (2) an aluminum diffusion zone (3), and on the surface of the blade substrate (2) arranged hard material coating (4). The compressor blade (1) of the preceding claim, wherein the hard coating (4) consists of TiN, TiAlN, AlTiN, CrN as single- or multi-layer ceramics or contains TiN, TiAlN, AlTiN, CrN as single or multi-layer ceramics. The compressor blade (1) of one of the preceding claims,
wherein the aluminum diffusion zone (3) has a thickness of 10 to 30 micrometers, preferably 15 to 25 micrometers. The compressor blade (1) of one of the preceding claims,
wherein the aluminum diffusion zone (3) has an aluminum content of 0.05 to 0.2 weight percent, preferably 0.075 to 0.15 weight percent. The compressor blade (1) of one of the preceding claims,
where the metal alloy is a creep-resistant steel. A compressor (105) for a gas turbine (100) and having a plurality of compressor blades (1),
wherein at least one compressor blade (1) of the plurality of compressor blades (1) according to one of the preceding claims is formed. The compressor (105) of the preceding claim,
wherein the plurality of compressor blades (1) are arranged in a plurality of rows, each row having a plurality of compressor blades (1) arranged transversely of a main flow direction of the compressor (105), and wherein the plurality of rows are arranged adjacent to the main flow direction in which the compressor blades (1) of the first to fourth rows of compressor blades (1) according to one of claims 1 to 5 are formed along the main flow direction. A manufacturing method of a compressor blade (1) according to any one of claims 1 to 5 and comprising the steps of: - Providing a blade substrate (2) made of a metal alloy; - diffusing aluminum into a surface zone of the blade substrate (2); and - Coating of the blade substrate (2) with a hard material coating (4). The manufacturing method of the preceding claim, wherein in the step of diffusing aluminum into the surface zone, an aluminum diffusion zone (3) having a thickness of 10 to 30 micrometers, preferably 15 to 25 micrometers, is produced. The manufacturing method of claim 8 or 9, wherein the step of diffusing aluminum into the surface zone is carried out such that an aluminum content of 0.05 to 0.2 weight percent, preferably 0.075 to 0.15 weight percent, is present in the surface zone , The manufacturing method of any one of claims 8 to 10, wherein in the step of coating the blade substrate (2) with a hard material coating (4), a step of physical vapor deposition or thermal plasma spraying is performed.

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